Claude review: drm/display: scdc_helper: Add HDMI 2.0 scrambling management helpers

[Claude Code Review Bot <claude-review@example.com>]

Patch Review

This is the core patch. Several observations:

1. **`drm_scdc_monitor_scrambler()` re-schedules unconditionally**: In `drm_scdc_setup_scrambler()`, the delayed work is always scheduled when called. If the monitor callback finds that scrambling status was lost and calls `drm_scdc_setup_scrambler()` again, it re-schedules itself, which is correct periodic monitoring behavior.

2. **`drm_scdc_reset_crtc()` accesses `connector->state` without holding locks**: The function reads `connector->state->crtc` and `crtc->state->active` outside of any modeset lock. While this is in a detect context where the connection_mutex may be held, the connector state access is still technically racy. However, this mirrors what `drm_bridge_helper_reset_crtc()` does in the existing codebase, so it follows established (if imperfect) patterns.

3. **`// TODO: Also handle HDMI 2.1 FRL link training`**: C++ style comment. Kernel style prefers `/* */`. Minor, but will likely get flagged by checkpatch.

4. **Error handling in `drm_scdc_start_scrambling()`**: The rollback on failure is thorough — cancels the work, clears the callback, and resets both scrambling and clock ratio on the sink. Good.

5. **`drm_scdc_sync_status()` early returns**: The function returns 0 when `hdmi->funcs` is NULL, and also returns 0 when scrambler callbacks are not set. This means non-HDMI-2.0 bridges silently succeed, which is the right behavior.

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